Magnesium: Three Field Uses
Objective: Keep magnesium’s three EMS jobs separate — eclampsia, torsades, severe asthma — and treat it as a respiratory depressant, not a benign mineral.
Why This Matters
Magnesium sulfate shows up in three very different protocols. Mixing the eclampsia infusion with the “push it like adenosine” reflex is how you drop a blood pressure and a respiratory drive. AHA 2025: mag may be considered for polymorphic VT with a long QT (torsades); routine mag is not recommended for polymorphic VT with a normal QT, and intra-arrest mag does not improve outcomes as a generic antiarrhythmic.
- Name the job before you open the vial: eclamptic seizure, long-QT torsades, or severe asthma per protocol.
- Eclampsia is an infusion (or IM if no IV) — not a slam. Have a BVM; mag drops the drive to breathe.
- You do not have a serum mag level. Watch the patient, not a lab you cannot draw.
- Which of the three jobs is this — eclampsia, torsades, or severe asthma?
- Eclampsia: mag first, not benzo first
- Torsades: unsynchronized shock if pulseless/unstable; mag if it is the long-QT polymorphic picture
- Watch the drive to breathe — have a BVM
1. Eclampsia
First-line for presumed eclamptic seizure (pregnancy or up to 6 weeks postpartum). ACOG/NAEMSP EMS guideline: IV loading infusion, IM split-dose if no IV. See eclampsia. This is not a 2-second push.
2. Torsades de pointes
- Polymorphic VT with a long QT is the mag indication (AHA 2025 Class 2b).
- Pulseless or crashing: defibrillate (unsynchronized). Mag does not replace electricity.
- Normal-QT polymorphic VT (ischemic “polymorphic”) is not a mag problem — treat ischemia and follow protocol antiarrhythmics.
3. Severe asthma
Adjunct in some protocols after bronchodilators for life-threatening bronchospasm. Not a substitute for albuterol, oxygen, or an airway plan. Infusion, not a casual slam, in most teaching pathways.
Toxicity
- Loss of reflexes, respiratory depression, hypotension, then arrest — a known obstetric dosing-error theme.
- AHA 2025: if a pregnant patient arrests on a mag infusion, stop the mag and give calcium.
- This site does not publish grams or rates. Protocol owns mixing. Label the bag.
Field Pitfalls
- Mag for every wide-complex tachycardia.
- Pushing an eclampsia load like an adenosine slam.
- No BVM ready.
Practice
60-second drill
Partner names: postpartum seizure; pulseless polymorphic VT; talking moderate asthma. Mag yes/no, and shock yes/no, in one breath each.
Related: Eclampsia, WCT, Albuterol.
Sources & Further Study
Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.
- NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language; protocol still wins
- AHA 2025 Part 9: Adult ALS — mag for torsades (long QT); not routine for normal-QT polymorphic VT; not a generic arrest drug
- AHA 2025 Part 10 — calcium if arrest on a mag drip in pregnancy
- ACOG/NAEMSP eclampsia EMS guideline
Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.
Check Your Understanding
Street decisions from this lesson only. After you check, the key is highlighted. Education practice — not a certification exam.